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Puzzle for the electronics gurus out there... failure in near vacuum enviroment.

Discussion in 'Electronic Basics' started by David Harper, Sep 30, 2003.

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  1. David Harper

    David Harper Guest

    I'm engaged in a high altitude project incorporating an automatic
    camera. In order to ensure that the potential cameras selected were
    capable of operating in a near-vacuum, two were tested in a vacuum
    chamber. One was a Kodak Ke60, and the other was a Samsung 80Ti.
    Both had leads soldered to the shutter contacts, which were controlled
    by solid state relays via a microcontroller. The 80Ti's only other
    modification was removal of the large flash cap, as we were not
    planning on using a flash (not that a flash at 100k ft would do any
    good anyway). The 80Ti operated throughout the test, while the Ke60
    failed at around 1 PSI. The standard "burned electronics smell" was
    present after opening the chamber.

    After opening the case to the Ke60 to determine what cause the Ke60
    failure, it looks like there was heating near the flash circuitry.
    Specifically, there is some discoloration near the contacts to a
    silver, eliptical-shaped capacitor (looks wrapped) with "333KS" on the
    side. Is this a pressure sensitive component? (the chamber went from
    14.7 PSI to about .05 PSI in about a minute, so it was rapid
    depressurization). The large flash cap was still good, so I don't
    believe this was the point of failure.

    Could it have been this 333KS component? If not, what potential
    components may have failed due to decreased ambient pressure?

    Thanks in advance for any advice!
    Dave
     
  2. John Fields

    John Fields Guest

     
  3. Baphomet

    Baphomet Guest

    Why not contact Kodak?
    http://www.kodak.com/global/en/service/contactKodak/digitalCameras.jhtml
     
  4. David Harper

    David Harper Guest

  5. David Harper

    David Harper Guest

    Yeah, that's a possibility. But I don't believe any of the components
    in the failure area depend highly on convection. In addition, it was
    only after the 3rd shot that the camera failed, with 20 seconds of
    time in between powering off and powering back up for a picture... I
    don't think that's enough time or a high enough duty cycle for a
    component to burn out...
     
  6. John Fields

    John Fields Guest

    ---
    If it's not that, then you may have lucked out ;^) and gotten a camera
    with a bad component.

    When you say the area around the "contacts" of the capacitor was
    discolored do you mean where the cap's leads were soldered into the PCB?
    If so, it could be that a high-resistance solder joint exists there and
    is heating up, possibly aggravated by the inability of the heat
    generated to be removed by convection. You may want to try either
    touching it up (the joint) with a hot iron and a little extra solder or
    solder-sucking it clean and re-soldering it. OTOH, the discoloration
    may have been caused by arcing occurring because of a combination of
    high voltage (the trigger pulse) and the low pressure allowing a cap to
    discharge across the PCB.
     
  7. John Fortier

    John Fortier Guest


    Dave,

    If you don't need the flash, why not just remove the components associated
    with it and re-test?

    I live in Rochester NY, home town of Kodak. Your experience with their
    customer "help" is. unfortunately, typical of the company as a whole.
    They are a company where filling dead shoes was the only way to gain
    promotion and who really haven't moved with the times. But they, somehow,
    still make damned good digital cameras!

    John
     
  8. Dbowey

    Dbowey Guest

    re: >But they, somehow,
    Starting when?

    Don
     
  9. Baphomet

    Baphomet Guest

    Dave -

    Something I have done in the past with great success (although not with
    Kodak) is to bypass customer support and engineering and go right to public
    relations. Tell them you are going to bad mouth them across the internet
    with bad publicity if you don't get satisfaction. The last thing in the
    world a smart company (and Kodak is that if nothing else) that spends
    millions on advertising wants is widespread negative publicity. Let customer
    relations do the leg work for you. That is what they get paid for.
     
  10. Guest

    When you removed all the air you removed the ability of the device to
    cool itself, thus it overheated.
     
  11. David Harper

    David Harper Guest

    Again, as mentioned in a previous post, I don't believe that happened.
    First, in a film camera, very few (if any) of the components depend
    highly on convection (try to find a heat sink anywhere in a film
    camera). In addition, it was only after the 3rd shot that the camera
    failed, with 20 seconds of time in between powering off and powering
    back up for a picture... I don't think that's enough time or a high
    enough duty cycle for a component to burn out, based on the heat
    capacity of even the small components. I've taken 36 shots in a 45
    second period in normal conditions in a test to determine how quickly
    it could take shots, and that'd tend to overheat any components much
    more severly that 3 shots in a near vacuum.

    Secondly, many other cameras are capable of operation in a vacuum, and
    have been used in similar enviroments. It was obviously some thing or
    some component specific to this design.

    Dave
     
  12. David Harper

    David Harper Guest

    <snip>

    How can low pressure increase the possibility of the cap discharging
    across the PCB? I'm under the impression that the absence or presence
    of air is almost negligible as far as any insulating conditions go...

    Thanks,
    Dave
     
  13. David Harper

    David Harper Guest

    <snip>

    Yeah, I looked into that. Unfortunately, it looks like the flash
    circuit is integrated closely into the other circuitry... in addition,
    being an ME (and not an EE) doesn't help. I think I might just remove
    the large flash cap and leave the oscillator circuit and the coil
    intact. Could that potentially eleviate the problem?

    Thanks,
    Dave
     
  14. John Fortier

    John Fortier Guest

    It could cause other problems, though. for example, the charger circuit
    senses the voltage on the cap and cuts off the oscillator when charging is
    complete. If there is no cap, then it will either not run at all, which is
    what you want, or run continuously, which is not desirable. The only way to
    find out id to do it and see what happens..

    If it runs continuously, you might try replacing the large cap with a small
    ceramic, which would be impervious to changes in air pressure and wouldn't
    hold enough charge to trigger the flash..

    One thought; if the large cap is an electrolytic, and it is vented rather
    than sealed, or if the sealing gave way, it would have dried out very
    quickly under vacuum conditions. This may, repeat, may have caused your
    problems.

    Regards

    John
     
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